The invention disclosed herein, in general, relates to a pseudorandom noise receiver and specifically relates to a method of differentiating between an auto-correlated weak signal and a cross-correlated product of weak and strong signals in a receiver used in global positioning system (GPS).
GPS satellites transmit signals to a universal receiver with a unique code called the coarse acquisition (C/A) code. The C/A code belongs to the family of gold code having a code length of 1023 chips. Signals from the satellites are coded with gold codes and transmitted at a chip rate of 1.023 MHz, with a period of 1 millisecond, with the code repeating every millisecond. Each satellite has a unique code for reception at the receiver. In correlation techniques, the incoming satellite signal is multiplied with a locally generated code. For example, the incoming satellite signal comprises a carrier of 1575.42 MHz, navigation data bits of 50 Hz and a coarse acquisition (C/A) code of 1.023 MHz.
Consider a case where the incoming signal from the satellite in a GPS receiver comprises a mix of weak and strong signals and where the weak signal is the desired signal and the strong signal is non-desired signal. There is a need to accurately differentiate between an auto-correlated weak signal and a cross-correlated product of weak and strong signals in a global positioning systems receiver. Interferences from the undesirable strong signals result in loss of valuable data transmitted from the satellite.